LT1309
500kHz Micropower
DC/DC Converter
for Flash Memory
FEATURES
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DESCRIPTIO
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60mA Output Current at 12V from 3V or 5V Supply
Shutdown to 9碌A
VPP VALID Comparator
Up to 85% Efficiency
Switching Frequency: 500kHz (Typical)
Quiescent Current: 650碌A
Low V
CESAT
Switch: 300mV at 0.5A (Typical)
Soft Start Reduces Supply Current Transients
Uses Low Value, Small Size,
Surface Mount Inductors
Available in 8-Lead SO Package
APPLICATI
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Flash Memory VPP Generators
Type II and III PCMCIA Card DC/DC Converters
3V to 12V, 5V to 12V Converters
Portable Computers and Instruments
Cellular Telephones
DC/DC Converter Module Replacements
The LT
廬
1309 is a 500kHz micropower DC/DC converter
for Flash Memory. The regulator features Burst Mode
TM
operation with a 0.5A, 300mV switch, enabling 85%
efficiency at the fixed 12V output. High frequency opera-
tion permits the use of small value, and therefore small
size, surface mount inductors and capacitors. The LT1309
comes in an 8-lead SO package allowing extremely
compact PC board layouts. These features make the
device attractive for PCMCIA cards, cellular phones and
other applications where PC board space is limited.
Quiescent current is 650碌A decreasing to 9碌A when the
part shuts down. The device includes a soft start feature
which limits supply current transients during turn-on.
The LT1309 contains a VPP VALID comparator with a
logic output that goes low when the output voltage is
ready to program 12V Flash Memory. This comparator
simplifies the interface to external control logic.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATI
V
IN
3.3V TO 5V
V
IN
VPP VALID
ON/OFF
12V, 60mA Flash Memory Programming Supply
L1*
10碌H
D1
鈥?/div>
86
VPP 12V, 60mA
84
82
EFFICIENCY (%)
V
SW
+
C1
4.7碌F
VPP VALID SENSE
LT1309
SOFT
ON/OFF
START
PGND
GND
80
78
76
74
72
V
IN
= 3.3V
R1
1M
C2
1碌F**
C3
0.1碌F
* MURATA ERIE LQH3C100K0YM00
** CERAMIC
鈥?/div>
MOTOROLA MBR0530
LT1309 鈥?TA01
70
1
10
LOAD CURRENT (mA)
100
LT1309 鈥?TA02
U
12V Output Efficiency
V
IN
= 5V
UO
UO
1
1
2
3
4
5
6
7
8
